The invention discloses a method for measuring 
gas pressure of a 
coal seam by a casing high-pressure hole sealing method. The method comprises the following steps: a, a hole is opened with a large-
diameter drill bit, the depth of a casing can be increased by drilling, and then the casing with a 
flange at the outer end is sent into the hole; b, 
expansive cement mortar is injected into the hole in a grouting mode to enhance the casing; c, after the 
expansive cement mortar is solidified, drilling is carried out with a 
drill bit which is one size smaller than the large-
diameter drill bit in step a along the original drilling center, the drilling is stopped when a 
coal seam is approached, and the 
expansive cement mortar is injected into a whole-hole section in a grouting mode for reinforcement after drilling cuttings are removed; d, after the expansive 
cement mortar is solidified, the hole is drilled with a 
drill bit which is one size smaller than the 
drill bit in step c along the original drilling center until the 
coal seam is penetrated; and e, the 
flange at the outer end of the casing is connected with a pressure gage to measure 
gas pressure. Large and small gaps and gap water around the 
drill hole can be effectively blocked in a high-
pressure grouting method, an 
air leak channel is sealed, and rapid and accurate 
pressure measurement is realized.